From fbbe32618e97eff81577a01eb7d9adcd64a216d7 Mon Sep 17 00:00:00 2001 From: Jia Yao Date: Thu, 5 Feb 2026 16:15:29 +0000 Subject: drm/xe: Add bounds check on pat_index to prevent OOB kernel read in madvise MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When user provides a bogus pat_index value through the madvise IOCTL, the xe_pat_index_get_coh_mode() function performs an array access without validating bounds. This allows a malicious user to trigger an out-of-bounds kernel read from the xe->pat.table array. The vulnerability exists because the validation in madvise_args_are_sane() directly calls xe_pat_index_get_coh_mode(xe, args->pat_index.val) without first checking if pat_index is within [0, xe->pat.n_entries). Although xe_pat_index_get_coh_mode() has a WARN_ON to catch this in debug builds, it still performs the unsafe array access in production kernels. v2(Matthew Auld) - Using array_index_nospec() to mitigate spectre attacks when the value is used v3(Matthew Auld) - Put the declarations at the start of the block Fixes: ada7486c5668 ("drm/xe: Implement madvise ioctl for xe") Reviewed-by: Matthew Auld Cc: # v6.18+ Cc: Matthew Brost Cc: Shuicheng Lin Cc: Himal Prasad Ghimiray Cc: "Thomas Hellström" Cc: Rodrigo Vivi Cc: Matthew Auld Signed-off-by: Jia Yao Signed-off-by: Matthew Auld Link: https://patch.msgid.link/20260205161529.1819276-1-jia.yao@intel.com (cherry picked from commit 944a3329b05510d55c69c2ef455136e2fc02de29) Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/xe/xe_vm_madvise.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c index add9a6ca2390..52147f5eaaa0 100644 --- a/drivers/gpu/drm/xe/xe_vm_madvise.c +++ b/drivers/gpu/drm/xe/xe_vm_madvise.c @@ -291,8 +291,13 @@ static bool madvise_args_are_sane(struct xe_device *xe, const struct drm_xe_madv break; case DRM_XE_MEM_RANGE_ATTR_PAT: { - u16 coh_mode = xe_pat_index_get_coh_mode(xe, args->pat_index.val); + u16 pat_index, coh_mode; + if (XE_IOCTL_DBG(xe, args->pat_index.val >= xe->pat.n_entries)) + return false; + + pat_index = array_index_nospec(args->pat_index.val, xe->pat.n_entries); + coh_mode = xe_pat_index_get_coh_mode(xe, pat_index); if (XE_IOCTL_DBG(xe, !coh_mode)) return false; -- cgit v1.2.3